1. Field of the Invention
The present invention relates to a hinge, and more particularly to a hinge with a floating pivot point or axis. Hinges of the type herein described find particular but not necessarily exclusive utility in orthopedic supports and more particularly in knee braces. More specifically, the present invention relates to a hinged knee brace for restraining a knee while permitting normal movement thereof, such as by restraining rotation and dislocation or subluxation of a tibia with respect to a femur in a wearer's leg.
2. Description of the Prior Art
Extensive studies have shown that the human knee joint is a complex mechanism, and that the knee does not provide a single axis of rotation between the femur (thigh bone) and tibia (leg bone). During flexing and extension of the leg, the axis of rotation between the femur and tibia moves laterally, defining a generally J-shaped path. This results from both a rotating and a sliding movement in the knee joint.
Any attempt to provide a knee brace that limits the movement of the limbs about a single axis not only causes discomfort to the wearer, but can cause damage to the knee joint. Where such a single-pivot axis brace is secured to both the thigh and the calf, a sliding movement along the leg is created, abrading the skin and causing substantial discomfort, as well as limiting effective leg movement.
Referring, for example, to U.S. Pat. No. 3,669,105, issued June 13, 1972, to I. F. Castigla for "Brace for Articulated Limbs," and a similar brace with an adjustable hinge as shown in U.S. Pat. No. 3,785,372, issued January 15, 1974, to W. A. Craig for "Extension Desubluxation Hinge Appliance," the single pivot axis shown causes the supporting pads to slide on the leg as the knee is flexed. To relieve such sliding movement, the pads are necessarily soft and flexible, thereby reducing the effectiveness of the brace.
A variety of devices have been developed in an effort to provide the complex pivoting movement associated with the knee joint, while at the same time providing the necessary support for the knee and leg. See, for example, U.S. Pat. No. 4,489,718, and published U.K. Pat. Appl'n No. GB2139896A. These various devices are complex and accordingly are necessarily heavy and cumbersome. In most instances, the devices severely limit the natural sliding and pivoting movement of the knee. Knee braces with double pivot point or polycentric hinges are shown in U.S. Pat. No. 4,271,831 and published European Patent Specification No. 0070411.
A number of prior art patents disclose multicentric hinges for leg and knee braces. See U.S. Pat. No. 4,320,747; U.S. Pat. No. 4,463,751; U.S. Pat. No. 4,379,463; U.S. Pat. No. 3,817,244; and U.S. Pat. No. 4,409,689.